| With the increasingly serious industrial pollution, environmental problem hasaroused great concern. Heavy metals are being more and more widely used inindustry，bring great pollution to the environment even endanger human healthseriously. And precious metal resources are so depleted and expensive that it’s fairlyurgent for people to develop an efficient method for eliminating heavy metal ionsfrom water, which can also effectively achieve precious metal recovery.Most of heavy metal polluted in water is in ionic form. Currently, the commonsolutions to solve heavy metal ions pollution are including: neutralization, sulfideprecipitation, oxidation reduction, electrolysis, ion exchange resins，adsorption and soon. Neutralization and sulfide precipitation method is simple and quick, but it willproduce secondary pollution, so that it could not completely solve the pollutionproblem. Ferrite and oxidation-reduction could recover heavy metal ions, but theirprocess is complex, the operation is more difficult. Electrolysis can also recycleheavy metal ions, but it takes high energy consumption. Ion exchange resin has bettertreatment capacity, and can get better effluent water quality, making it the mostcommonly used method in current, but it could not easily to be recycled, and it is easyto poisoned and aging. The adsorption method is widely research and application forits simple and quick. The operation of activated carbon adsorption is relatively simple,and heavy metals can be recycled too, but activated carbon is easy to be inactivated.The of low-cost adsorption materials such as plant residues, cinder, plantseeds skin, peel, seaweed, are abundant in resources and cheap, butthese materials require complex pre-processing, and most of them areone-time adsorption material, and it may produce secondary pollution. Therefore, ifwe can find a material which could separation quick, simpleoperation, regeneration and recycle of heavy metal, adsorption wouldeffective treatment of heavy metal waste water, and recovery of precious metals.Magnetic beads which have high specific surface area, instant magnetic responseand could be easily modified with various functional groups, etc., have been appliedin many areas to separate the target production. In this paper, the ethylene diamine modified polymer magnetic beads weresynthesized by microsuspension polymerization, and were used to the separation andrecovery of heavy metal ions aqueous solution. The conditions of the adsorption,desorption, regeneration and the mechanism were investigated and optimised. Theresults are as following:1、 The micro-sized superparamagnetic polymer beads were synthesized bymicrosuspension polymerization, and was sufficiently modified with ethylenediamine. The surface area, surface morphology, N content and magnetic content werecharacterized carefully. The results show that amino-modified polymer magneticbeads have a larger surface area, good mono-dispersity, plentiful functional groupsand large magnetic content.2、 The magnetic beads were applied to adsorb metal ions and adsorptionconditions were investigated carefully. The saturation adsorbance of Cd2+, Co2+, Ni2+,Cu2+onto magnetic beads were67.7mg g-1,50.0mg g-1，47.6mg g-1and50.6mg g-1,respectively. The adsorption process could be carried out at room temperature, pH=3~6, and could be completed within5min. The concentration of heavy metals in theeffluent water turned out to be below the national integrated wastewater dischargestandard.3、 The desorption and regeneration conditions were investigated carefully. Andit was found that98%heavy metal ions on the magnetic beads could be desorbed inthe acid solution, its operation condition was simple, the process could be completedquickly, and the concentration of acid solution required are lower. Magnetic polymerbeads which have adsorbed heavy metal ions could be easily regenerated in alkalisolution, the adsorption capacity could be revived more than95%, and itsregeneration process is simple, fast and efficient in alkali solution at lowconcentration. The, magnetic polymer beads were proved to have good renewableperformance.4、 Because of ethylene diamine modification process is carried out at highertemperatures, the surface structure of these magnetic beads becomes so stable, thatslow down the corrosion of magnetic beads in the acid and alkali solution. Hence, itensured that the magnetic beads have good adsorption capacity. The adsorption capacity of these magnetic beads remained almost unchanged within15cycles ofadsorption-desorption-regeneration, and has some adsorption capacity after applying35times.5、 Several adsorption models were used to describe the adsorption process forstudy of the mechanism. Langmuir equation well fitted the adsorption data of thesemetal ions, it means the adsorption of heavy metal ions onto these magnetic beads ismonolayer chemical adsorption.Compared with activated carbon adsorption, ion exchange resins and othermethods, magnetic polymer beads used as adsorbent to recovery heavy metal ions hasmany advantages, such as, simple operation, easy to use, fast and efficient, recyclable,easy regeneration, good effluent water quality, stable structure and property. Hence, indealing with heavy metal waste water, amino-modified magnetic polymer beads havea good prospect. |
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